import math
x1,y1,x2,y2 = map(float, input().split())
a1 = (x2-x1)**2
a2 = (x1-x2)**2
b1 = (y2-y1)**2
b2 = (y1-y2)**2
if x1<x2:
    if y1<y2:
        print(math.sqrt(a1+b1))
    else:
        print(math.sqrt(a1+b2))
else:
    if y1<y2:
        print(math.sqrt(a2+b1))
    else:
        print(math.sqrt(a2+b2)) import math math x1,y1,x2,y2 = map(float, input().split()) x1 map(float, input().split()) map float input().split() ().split () input split y1 x2 y2 a1 = (x2-x1)**2 a1 (x2-x1)**2 x2-x1 x2 x1 2 a2 = (x1-x2)**2 a2 (x1-x2)**2 x1-x2 x1 x2 2 b1 = (y2-y1)**2 b1 (y2-y1)**2 y2-y1 y2 y1 2 b2 = (y1-y2)**2 b2 (y1-y2)**2 y1-y2 y1 y2 2 if x1<x2:
    if y1<y2:
        print(math.sqrt(a1+b1))
    else:
        print(math.sqrt(a1+b2))
else:
    if y1<y2:
        print(math.sqrt(a2+b1))
    else:
        print(math.sqrt(a2+b2)) x1<x2 x1 x2 if y1<y2:
        print(math.sqrt(a1+b1))
    else:
        print(math.sqrt(a1+b2)) y1<y2 y1 y2 print(math.sqrt(a1+b1)) print math.sqrt(a1+b1) math.sqrt math sqrt a1+b1 a1 b1 print(math.sqrt(a1+b2)) print math.sqrt(a1+b2) math.sqrt math sqrt a1+b2 a1 b2 if y1<y2:
        print(math.sqrt(a2+b1))
    else:
        print(math.sqrt(a2+b2)) y1<y2 y1 y2 print(math.sqrt(a2+b1)) print math.sqrt(a2+b1) math.sqrt math sqrt a2+b1 a2 b1 print(math.sqrt(a2+b2)) print math.sqrt(a2+b2) math.sqrt math sqrt a2+b2 a2 b2 b2 = (y1-y2)**2 (y1-y2)**2 b2 b1 = (y2-y1)**2 (y2-y1)**2 b1 y1,x2,y2 = map(float, input().split()) map(float, input().split()) y1 y2 = map(float, input().split()) map(float, input().split()) y2 a2 = (x1-x2)**2 (x1-x2)**2 a2 x1,y1,x2,y2 = map(float, input().split()) map(float, input().split()) x1 x2,y2 = map(float, input().split()) map(float, input().split()) x2 a1 = (x2-x1)**2 (x2-x1)**2 a1
import math
x1,y1,x2,y2 = map(float, input().split())
a1 = (x2-x1)**2
a2 = (x1-x2)**2
b1 = (y2-y1)**2
b2 = (y1-y2)**2
if x1<x2:
    if y1<y2:
        print(math.sqrt(a1+b1))
    else:
        print(math.sqrt(a1+b2))
else:
    if y1<y2:
        print(math.sqrt(a2+b1))
    else:
        print(math.sqrt(a2+b2))
